You cannot use [ MF Assist] when shooting movies.
[43] How to Use Using shooting functions Adjusting the focus
Lock-on AF
Set up the tracking function to continue focusing on the subject.
1. MENU → (Camera Settings) → [Lock-on AF] → desired setting.
Menu item details
Off:
Does not track a subject to be focused on.
On:
Tracks a subject to be focused on.
[44] How to Use Using shooting functions Adjusting the focus
Lock-on AF (On)
Maintains the focus on a moving subject automatically.
1. MENU → (Camera Settings) → [Lock-on AF] → [On].
2. Align the target frame and the subject to be tracked, and press in the center.
Note
The [Lock-on AF] function may not operate well in the following situations: